Friction welding is a known process for joining and repairing parts such as those of iron, aluminum or other suitable metals as well as many plastic materials utilizing the heat of friction to plasticize the interface of relatively rotating components and then allowing the interface to cool and fuse so that the components are metallurgically integrated and securely joined together. In one aspect of friction welding, frequently referenced as friction stir welding, a rotating stir weld tool of temperature stable material is pressed into a joint or seam between abutted parts to be stir welded together. The axially loaded tool is then moved along the joint to effect the localized frictional heating of a strip of materials along the joint including the interface materials sufficient to effect their softening and the metallurgical intermixing. These parts fuse and securely weld together at the seam when the tool is removed and the intermixed material solidifies.
Another aspect of this part joining technique, often termed as friction plunge fastening or friction-stir fastening, can be carried out with the employment of rotating fasteners generically referenced in this application as friction stir rivets to connect overlaying parts. Such rivets, of a temperature stable material generally have enlarged heads with slots or other configurations to drivingly fit with a separate rotatable driver of an installation tool and to accommodate the torque as well as the axial load of the tool. These rivets further have profiled shank portions axially depending from their heads to frictionally engage and then progressively heat and bore into the overlap of the parts being joined.
More particularly, the shanks of these rivet constructions are frictionally introduced into the material of the parts such as at predetermined points on overlapped edge portions and at predetermined ranges of rotational speeds and loads. Frictional heat is generated as the rotating fastener physically works the material of the parts to create a plasticized region of material in the overlap surrounding the rotating shank. The parts are joined on the termination of fastener rotation and frictional heating so that the softened or plasticized material of the parts cools and solidifies around the fastener shank to effect the connection. In some instances diffusion bonding may take place between the outer surfaces of the fastener shank and the material of the joint when the plasticization points of the interfaces of the rivet and that of the parts being connected are metallurgical compatible.
Prior friction-stir fastening do not meet new and higher standards and objectives for machines and methods providing optimal high production rates that feature consistent superior quality friction-stir fastening and joining of parts.